Senate Republicans expect to include a repeal of the Obamacare individual mandate, which requires people to purchase health insurance or face penalties, in their tax plan, complicating the party's efforts to reshape the tax code by year's end.

The change -- which President Trump called for yesterday in a surprise tweet from Asia -- would help Republicans pay for proposed tax cuts in their plan by slashing more than $300 billion in government spending on subsidized medical coverage over 10 years.

The move would also leave 4 million more Americans without health insurance by 2019 and 13 million by 2027, according to the nonpartisan Congressional Budget Office.

Slipping the health care provision into the tax plan carries risks for Republicans.

Doing so could ignite Democratic opposition to the tax bill and turn the tax push into a health care debate, complicating the GOP's top legislative priority and making it more difficult to achieve by the end of the year.

The House is expected to vote on its version of the tax plan -- which won't include the individual mandate repeal -- as soon as Thursday.